Mixing machine



FIG. 1 is a front-right side perspective view of a mixing machine showing my new design;

FIG. 2 is rear-right side perspective view thereof;

FIG. 3 is a front-left side perspective view thereof; and,

FIG. 4 is a rear-left side perspective view.

The broken lines shown in the drawings are for illustrating portions of the mixing machine that form no part of the claimed design. 

The ornamental design for a mixing machine, as shown and described. 